Floating roof tanks are used throughout the world to store a variety of liquids, some of which emit pollution causing vapors which must be contained with the tank. Floating roofs require support above the tank bottom when the tank is not in service to provide clearance for piping and so that construction and maintenance crews can access the tank beneath the floating roof.
It is desirable to provide more than one roof support position. A low position, one to three feet above the tank bottom, is needed in many tanks due to piping or conduits that may be located near the bottom of the tank. A high position is desirable to permit access for workers to clean and repair the interior of the tank. A single high position does not permit the tank to function properly due to the accumulation of vapor in the tank when the liquid level falls below the high position.
Early floating roof supports functioned well as structural members but were typically expensive to manufacture and had openings through which vapors could escape from the tank. A variety of methods were employed to seal the openings that were unsatisfactory because they were expensive, unsightly, or prone to deteriorate when exposed to some tank vapors or sunlight.
It is the general object of this invention to provide a floating roof support for reduced vapor loss that is adjustable between a low position and a high position and is inexpensive to fabricate and install.